From 6b72dd82231c8e35c3c90bbc941d02fc771a9121 Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Thu, 26 Nov 2015 10:14:04 +0100
Subject: [PATCH] Remove `Lock` structure again as we changed design

---
 posts/DRAFT-paging.md    | 14 --------------
 src/memory/paging/mod.rs |  8 --------
 2 files changed, 22 deletions(-)

diff --git a/posts/DRAFT-paging.md b/posts/DRAFT-paging.md
index 9d9e627c..46f57507 100644
--- a/posts/DRAFT-paging.md
+++ b/posts/DRAFT-paging.md
@@ -14,22 +14,8 @@ When accessing a `P2` table, we only loop two times and then choose entries that
 
 The math checks out, too. If all page tables are used, there is 1 `P4` table, 511 `P3` tables (the last entry is used for the recursive mapping), `511*512` `P2` tables, and `511*512*512` `P1` tables. So there are `134217728` page tables altogether. Each page table occupies 4KiB, so we need `134217728 * 4KiB = 512GiB` to store them. That's exactly the amount of memory that can be accessed through one `P4` entry since `4KiB per page * 512 P1 entries * 512 P2 entries * 512 P3 entries = 512GiB`.
 
-## A Safe Module
-We need to make sure that the page tables can't be modified concurrently. So we must ensure exclusive access for all functions that modify the page table. For a normal struct, Rust would handle it at compile time through the `&` and `&mut` rules. But since we have some magic memory address instead, we must do some manual work.
 
-To ensure exclusivity, we introduce a `Lock` struct. All operations that modify the current page table borrow it exclusively (`&mut`) and all operations that just read the table borrow it through `&`. That way, we benefit from Rust's aliasing rules.
 
-The `Lock` struct looks like this (in a new `memory/paging/mod.rs` module):
-
-```rust
-pub struct Lock {
-    _private: (),
-}
-
-impl !Send for Lock {}
-impl !Sync for Lock {}
-```
-The `_private` field is needed to forbid construction from outside. The `!Send` and `!Sync`
 
 ## Switching Page Tables
 
diff --git a/src/memory/paging/mod.rs b/src/memory/paging/mod.rs
index 3f7d97ae..e69de29b 100644
--- a/src/memory/paging/mod.rs
+++ b/src/memory/paging/mod.rs
@@ -1,8 +0,0 @@
-/// The paging lock must be unique. It is required for all page table operations and thus
-/// guarantees exclusive page table access.
-pub struct Lock {
-    _private: (),
-}
-
-impl !Send for Lock {}
-impl !Sync for Lock {}